Various techniques are proposed with regard to a head-up display (HUD) for displaying an image on a windshield of a vehicle. For example, proposed is a HUD for displaying an image as a virtual image as if it really existed in a real landscape in front of the vehicle seen from a driver. For example, Patent Document 1 proposes a HUD which changes a distance between an apparent position of a virtual image and a driver in accordance with a vehicle speed.